Electronmicroscopic Examination of Corroded Aluminum-Copper Alloy Foils

The formation of particles of copper through selective dissolution of dilute Al-Cu solid solutions in sulfuric acid was studied by transmission electron microscopy of foils prethinned before corrosion. A technique was employed for prethinning without surface enrichment. At -500 mV vs. SCE, a significant fraction of the copper made available by selective dissolution appeared as particles, but not at -100 mV vs. SCE. The results are discussed with reference to concurrent AES observations on the Cu-enriched solid solution beneath the anodic film over the main body of the electrode.